Allow recording of messages even on hang up
Added users table for storing user details
Added user registration to the call flow

Users can now register, as per issue #1 as well as handling
for non registered users is there as per issue #5
Added functionality to only have new messages

Functionality for only listening to new messages is now added.
System keeps track of messages that each user has listened to
and will return only those which has not been listened to yet.